This invention relates to a method for pain relief and to electrical stimulation systems for generating random pulse trains to be used for pain relief.
The existence of inhibitory neurons in the pain-transmitting nervous system in mammalian bodies is well known. Percutaneous electrical stimulations of dorsal column and/or peripheral nerves sometimes successfully produce selective excitation of inhibitory neurons in substantial gelatinosa or other ganglia in the central nervous system, resulting in temporal abolition of pain.
A typical pulse train conventionally used for the stimulation is depicted in FIG. 1, in which stimulation parameters such as pulse rate, pulse width and pulse amplitude do not change in time course. After a long-time use of such a stimulation which adopts uniform or simple periodic stimuli, the nervous system reveals adaptation effect against the stimuli. The monotony of the pattern is thought to be one of the reasons that the pain suppression effect diminishes in the long course of time.
For this reason, the stimulation pattern should be more variable and possibly be more comfortable.
The object of this invention is to provide a system which may produce a irregular stimulation by modulating pulses with random signals to give fresh sensations to the nervous system ceaselessly.